Twilight had no idea how Thunderbolt had fit, but now he was inside her he felt ten times bigger than before. "W-What's happened?" She looked down at her belly, expecting to see something, and almost jumped at how much her tummy had swelled.
"Tied. Expanding tips. Give it some time." Thunderbolt couldn't stop himself from purring if he'd tried—not that he wanted to try. "That was amazing."
It was impossible not to blush. Twilight certainly was surprised at getting a compliment. "But I didn't really do anything."
"You didn't just lay there. You moved with me. You were part of it." Thunderbolt squeezed Twilight a little with his wing. "Next time we'll do things a little different. You can be on top if you li—"
"N-No. I like having you there." Unable to blush more, Twilight settled on running through events in her mind. The sex had been—without a doubt—the best she'd had with a male. She corrected that to it being the best sex she'd had period. But she wasn't here just to enjoy herself, despite what Tree had said. "Actually, I'd like to try a few things, but not before we—we fuck like that a few more times." The purring, a rumble Twilight both heard and felt all the way down her spine, let her know exactly how much Thunderbolt liked the idea.
"I'd like that." Thunderbolt ran his claws, carefully, through Twilight's coat. "It shouldn't be much longer until I shrink down. I still don't know how I fitted all the way in. It shouldn't be possible."
"Magic seems to be the answer everyone uses for anything strange lately. Who cares about not possible if magic can be used." Twilight didn't like doing that, of course, but she was too excited for a round two to let physics get in the way.
There was always a moment, for Thunderbolt, when he felt a slight twinge in his groin as his body adjusted the blood flow so that his shafts would start to deflate. It was always both a happy and melancholic feeling—it heralded the end of that particular union, but was also a possible harbinger of more to come. "I'm going down now."
"Huh?" Moments after asking, however, Twilight felt what Thunderbolt meant. The stretching deep in her body started to go down. Part of her was relieved at having the odd pressure reduce, while part of her was a little sad. Fullness, Twilight Sparkle decided, was nice. "Oh."
"Don't try to rush it. I still have all those spikes, remember." Angling his head just right, Thunderbolt managed to nibble on one of Twilight's ears despite its attempts to twitch and flick away from him.
"He just—he fucked me and left. Just ran away and left me there." Twilight was so comfortable and felt so appreciated that she didn't even feel like crying. "I know he has some trouble with one of those parasites, but—"
"I have one of those in my head too. It doesn't make you a do bad things, it just makes you want to do a lot of things." Thunderbolt swapped ears, catching the other unawares. "Fun things," he said from the corner of his mouth while he kept his hold on the twitchy ear.
Despite how strange it felt to have her ears be sucked and nibbled, Twilight adored the sensation primarily because it was a show of care, and she well remembered the sort of teeth Thunderbolt had, and could extrapolate how careful he was being from that.
Twilight paused a moment, pondering if she should go further with the topic, then decided it was time to actually address the elephant in the room. "I've been thinking of infecting myself." So far, Thunderbolt was the only person Twilight had been willing to talk to about it. "Seeing the effects on Rainbow, I just—She recalls things so much easier. Everything. I didn't know Marble before she got infected, but she's the same. There's no detail she forgets."
"Though I bet they both forget a lot of things at particular times a day." Thunderbolt slid his big hand-talon along Twilight's chest and down to her belly. "I for one am glad I'm not stuck with just paws. They were good for running on, but inconvenient when it came to masturbation."
"You masturbate?" Twilight felt a little shocked.
"I get horny three or four times a day. Tree is obliging—Is obliging the right word?"
Twilight felt a giggle bubble up through her before it left her lips. Sex was awesome, but she was discovering pillow talk to be something she also enjoyed. "If you mean she helps you out with sex, obliging would be right."
"She obliges me as much as she wishes, but it's not enough. Even with Rainbow helping—and she really helps—I need more. I have two hands, which is fortunate."
"You have me, too." Twilight giggled and tilted her head back so she could press her snout under Thunderbolt's jaw. Deep inside her, she felt something give, then some more. "I think you're going down."
Thunderbolt purred a little louder and held Twilight to himself snugly. "In a little bit I could pull out without causing any soreness."
"But you could stay in a little longer?" Twilight clenched down on the smooth muscles of her rectum and vagina, massaging the shrinking shafts within. "It feels nice."
Petting her from the front of her chest all the way to her teats, Thunderbolt kept up his purring while Twilight kept up her slow squeezing of him. It wasn't sex—not how he was used to—but it felt good.
All good things, however, come to an end. Thunderbolt felt a point at which his shafts were starting to withdraw into his body and let out a soft sigh. "This ride is over—for me at least."
Twilight arched her spine and squirmed as Thunderbolt withdrew from her completely. She felt stretched and puffy still, but there was also a sense of chill on her sensitive parts. Nothing she could do would stop the little whine of loss from escaping her throat, but she was curious at what was still bloated.
Looking along her belly, Twilight noticed she still had a bump. "W-What's still inside—oh!" Blushing furiously, she'd never considered that she could either have so much fluid inside her that it would make her swell up, or that there was a chance of her getting pregnant. "Th-Thunderbolt? H-Have you checked to see if we're—well—fertile?"
"Fertile?"
Thunderbolt, Twilight realized, wasn't fully educated even if he did have a diverse vocabulary in some aspects. "Uh, babies. Puppies. Foals…"
"Oh!" Thunderbolt smiled in understanding, then his face fell. "You don't want puppies?" He looked at Twilight's swollen belly and shook a little.
Closing her eyes and rubbing her forehead, Twilight tried to focus on the problem. Doing so, while she could still feel all of his semen inside her, was not easy. "Okay. First thing is to not panic. Panicking isn't helpful. Easy for me to say that when I don't—Stop. Ugh!" She slowed her breathing in an attempt to stop her freak-out. "There's an easy way to tell if we're fertile. I need to get a blood sample from both of us and examine it. Uh… how do I get all this, um, out?"
Trying to calm himself so he didn't panic Twilight more, Thunderbolt focused on what she said. "Plug thing. Some of my stuff hardens for a bit. Normally a few hours and it will dissolve."
"Wow. Uh, do you think we could fly back to my place? I can do the test there." Twilight shifted her weight and rolled to her hooves. Standing up felt odd—she could feel how full he'd made her.
Wrapping both his forelegs around Twilight, Thunderbolt hugged her carefully to his chest. A jump and a pump of his wings shot him skyward while he held something precious tight. "Where is your house?"
"The shared house, remember?" Twilight pointed toward the city—vaguely in the direction of the big house she shared with her friends.
Landing as gently as he could, Thunderbolt set Twilight down in the back yard and felt more worry sneak up on him. Chief among his worries was that he'd done something that Twilight might take as hurting her, but he was also simply upset that he'd upset her. "How long will the test take?"
"Well, it's not just one test. There's a series of tests that could prove that we're infertile, and I'll start with the fastest ones." She didn't even pause to cast the spell that let her see with magic glasses. "I share the basement with Marble—we're trying to not double up on lab Equipment."
Thunderbolt let out a curious little rumble of assent. "What do you do with all of it?"
"Well, sometimes I make electronic things. You should see the drone I've been working on. Oh, and Marble and I made this machine that lets people record and play back physical emotions. Of course, we've mostly used it for naughty stuff, but it works really well." Opening the door to the basement, every step Twilight took reminded her that she was literally plugged full of Thunderbolt's seed. Part of her wanted to roll around on her back at how naughty and good it felt while another part was still freaking out that it could be getting her pregnant right as she was thinking about it.
Descending after Twilight, Thunderbolt closed the doors behind him. "What do you need from me?" He watched as Twilight tore open a syringe and lined it up on her own foreleg. The sight of blood reminded him of when he'd attacked Adagio.
"Right now? Blood and semen. The easiest test I can think of is to see if my antibodies attack your sperm." Twilight fetched another syringe and a little cup. "Um, do you think you could fill this?"
At the sight of Twilight holding out a tiny cup with that offer, and actually smiling, Thunderbolt couldn't help but smirk. "We both know I could. Take blood first." Thrusting out a foreleg, he offered it without worry.
"Do you—uh—want help?" The honest truth was, Twilight was curious about Thunderbolt's anatomy. Of course she'd had it inside her, and it had been very effective, but she wanted to see it all up close.
"Don't you have tests to perform?" Thunderbolt had recognized a playful tone, and given the worry that had been boiling in his blood, a little venting seemed a good idea.
Twilight let out the most defeated sigh of her life. Masturbating her dragon boyfriend wasn't just something kinky, it was science, but she'd have to wait to do that. "I'm gonna claim a raincheck on that, okay?" At Thunderbolt's clueless look, Twilight giggled. "A raincheck means it's something I plan to do later."
Thunderbolt began to purr again, even when Twilight jabbed the needle into his foreleg with her magic. He watched as the syringe filled with his green blood. "I tried to figured out why my blood was green, but I couldn't—"
"Copper. Most creatures have red blood that's based on iron in it. Hemoglobin is red. You must have copper-based blood. You must have hemocyanin, or something like it. It's pretty." Twilight blushed at calling Thunderbolt's blood pretty. "I mean, technically this is definitive proof that we aren't compatible, but I'll still do an antibody test at least."
The relief Thunderbolt heard in Twilight's words made him smile a little wider. She looked and sounded more relaxed now. "You just want to see me masturbate." His previous confidence returned, and the blush he saw in Twilight's cheeks, spurred on Thunderbolt. There wasn't really enough room in the basement for him to stand up and rub himself, so he rolled over to his back.
Twilight almost dropped everything at the sight of Thunderbolt's twin shafts on display. Her breath caught in her throat and she wanted—wanted more than anything—to climb up on his belly and ride them again. She had to shake her head and start processing her blood. "I'll just separate out the red blood cells…"
Thunderbolt realized that he couldn't and probably shouldn't distract Twilight from her work too much. Balancing the little cup on his chest, he closed his eyes and remembered back to being on top and inside her. Grasping each of his shafts carefully, he began to stroke himself.
Deliberately ignoring the huge dragon getting off in her basement wasn't easy for Twilight. The sound of both his talons working his shafts was a repeating, visceral noise that made everything under her tail clench a little, but what really hit her hard was the smell. Horny dragon, it seemed wasn't just a strong odor, it was one she found herself liking.
The moment Twilight had her own blood sample in the centrifuge, she spun around so quickly she almost fell over. The sight of Thunderbolt watching her while he got off somehow made it even better. She took a step toward him, then another. Closing her eyes, Twilight tried to detach herself from the situation, but all that did was sharpen her hearing and olfactory sense.